Browsing by Author "Jasna Sherin, P T."

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    Pink pigmented facultative methylotrophs (PPFMs) from chilli(capsicum frutescens) for biotic and abiotic stress migration and plant growth promotion
    (Pink pigmented facultative methylotrophs (PPFMs) from chilli(capsicum frutescens) for biotic and abiotic stress migration and plant growth promotion, 2025) Jasna Sherin, P T.; Anurajan, S
    Chilli, often referred to as the "wonder spice," is one of the most commercially valuable vegetable crop worldwide. Drought, a significant abiotic stressor, can cause substantial reductions in chilli crop yields and quality, resulting in significant economic losses. PPFMs have been shown to promote plant growth by producing plant growth regulators, altering agronomic traits, and improving water status, photosynthetic rates, and antioxidant enzyme activities. The study entitled “Pink Pigmented Facultative Methylotrophs (PPFMs) from chilli (Capsicum frutescens) for biotic and abiotic stress mitigation and plant growth promotion " was carried out during the period from 2023-2024 at College of Agriculture, Vellayani, Thiruvananthapuram, with the objective of isolation, screening and characterization of Pink Pigmented Facultative Methylotrophs (PPFMs) from chilli (Capsicum frutescens) and their evaluation for plant growth promotion with special emphasis on biotic and abiotic stress management. Thirty-five PPFM colonies were isolated from chilli phyllosphere using leaf imprint and serial dilution methods on AMS agar medium supplemented with 0.5% methanol and 10 μg cycloheximide and amended with 5% PEG 6000. These isolates were tentatively identified based on their pink pigmentation and further characterized by colony morphology, Gram reaction, and biochemical tests. Twenty-three PPFM isolates were selected for in vitro screening to assess their plant growth promoting abilities. IAA production among the isolates exhibited significant variability, ranging from 0.97 μg mL⁻¹ to 18.26 μg mL⁻¹ of culture filtrate. Isolate CF7 demonstrated the highest IAA production (18.26 μg mL⁻¹), followed by CF6 (13.60 μg mL⁻¹). All isolates produced varying amounts of gibberellic acid, ranging from 1.71 to 22.07μg mL-1. The highest gibberellic acid production was recorded in CF7 (22.07μg mL-1) followed by CF6 (21.35μg mL-1). Extracellular ammonia yield varied significantly, ranging from 0.27 to 10.06 μmol mL⁻¹. The isolate CF15 demonstrated the highest ammonia production (10.06 μmol mL⁻¹). ACC deaminase activity by different isolates ranged from 0.94 to 14.08 μg mL⁻¹, PPFM 38 (19.35 μg mL⁻¹) showed the highest activity followed by CF7 (14.08μg mL⁻¹). While all isolates grew in N-free malate bromothymol blue media, Waksman Base No. 77, and Jensen’s media, none demonstrated phosphate solubilization or antagonistic activity against phytopathogens. Based on Index ranking eight isolates were selected for primary assessment of drought tolerance potential in vitro. To evaluate drought tolerance potential in vitro, isolates were grown in media containing varying concentrations of PEG 6000. All isolates tolerated up to 30% PEG 6000. The isolates CF6, CF7, and CF15 were ranked based on drought tolerance in vitro for further studies. PCR amplification confirmed the presence of mxaF gene in these isolates, with an expected band size 550 bp indicating their ability to oxidise methanol using the methanol dehydrogenase enzyme (MDH). Molecular identification based on 16S rRNA sequencing of the isolates CF6, CF7, and CF15 showed maximum percentage identity to Methylorubrum populi, Methylorubrum thiocyanatum, and Methylorubrum podarium respectively. A pot culture experiment was conducted with chilli plants to assess the effects of PPFM isolates on plant growth promotion and drought tolerance. The experiment was a completely randomized design (CRD) with eight treatments and three replications which included four PPFM isolates (CF6, CF7, CF15, and reference culture PPFM 38), a consortium, and three control treatments (sterile water, AMS broth, and absolute control). Treatments were applied through seed treatment and foliar spray at 25th day after transplanting. The study demonstrated that application of PPFM isolates significantly enhanced plant growth parameters of chilli. The biometric parameters like maximum number of leaves (133.67), number of branches (4.50), shoot length (56.88 cm), dry weight of shoots (17.04 g), number of fruits (14.17) and yield per plant (53.45g) were recorded with CF6 treatment. Number of flowers (16), root length (35.42cm), fresh weight of roots (30.99g), and dry weight of roots (4.89g) were greater for CF15 treatment. PPFM 38 (81.83g) and CF6 (76.25g) recorded maximum fresh weight for shoots. The least parameters were recorded with either one or more of controls. Cell membrane integrity (82.3%), relative water content (85.52%), proline (86.51μg g-1tissues), SOD activity (0.44 activity g-1 min-1) and peroxidase (38.81activity g-1 min-1), were highest with PPFM 38 and CF6. The results suggest that Application of PPFMs through seed treatment and foliar spray (1%), can effectively improve growth and drought tolerance in chilli plants. Further research under field conditions is required before these can be developed as a bioformulation for sustainable agriculture.